feat(maestro): attach files in structured views

crates/maestro-daemon/src/session.rs

@@ -604,6 +604,36 @@ impl SessionManager {
         Ok(Some(replay))
     }
 
+    /// Store attachment bytes for a live structured session.
+    pub async fn store_acp_attachment(
+        &self,
+        id: Uuid,
+        name: &str,
+        bytes: &[u8],
+    ) -> Result<Option<std::path::PathBuf>, SessionError> {
+        {
+            let sessions = self.inner.sessions.lock().await;
+            let record = sessions.get(&id).ok_or(SessionError::NotFound(id))?;
+            if !record.is_live_structured() {
+                return Ok(None);
+            }
+        }
+        let dir = self.inner.sidecar.dir().join(format!("{id}.attachments"));
+        tokio::fs::create_dir_all(&dir).await?;
+        let dir = tokio::fs::canonicalize(dir).await?;
+        let path = dir.join(format!("{}-{name}", Uuid::new_v4()));
+        let mut file = tokio::fs::OpenOptions::new()
+            .write(true)
+            .create_new(true)
+            .mode(0o600)
+            .open(&path)
+            .await?;
+        use tokio::io::AsyncWriteExt;
+        file.write_all(bytes).await?;
+        file.sync_all().await?;
+        Ok(Some(path))
+    }
+
     /// Subscribe to the two projections of a structured session's ACP log.
     ///
     /// The transcript snapshot and whole reduced state are folded once by the